"Rule #1 in MoI: Never delete a construction curve :) Assign it a unique color, then hide it."

Thanks, will keep that in mind! :)

Tried a "best of both world" approach of keeping the construction rectangles and fixing the faces, so the points can also directly be edited. That doesn't work though, replacing the faces deletes the history connection. Ok, nevermind, one way to achieve something is enough.